Noise reduction in a power supply is an important matter because of increase in signal speed and decrease in a voltage of a power supply. In particular, in a decoupling circuit, an impedance property up to a high-frequency region needs to be taken into consideration, and anti-resonance (parallel resonance) between capacitors and between a power supply line and a capacitor may occur to become a problem in some cases.
PTL 1 discloses a multilayer wiring substrate enabling power supply impedance to be reduced at an anti-resonance frequency. A plurality of decoupling capacitors are connected in parallel to each other between a power supply and ground in the multilayer wiring substrate. The plurality of decoupling capacitors are constituted of a laminated ceramic capacitor connected by a wiring pattern including a resistance pattern having a predetermined resistance value, and a laminated ceramic capacitor connected by a wiring pattern not including a resistance pattern.
PTL 2 discloses a multilayer wiring substrate enabling power supply impedance to be reduced at an anti-resonance frequency. A plurality of decoupling capacitors connected in parallel to each other between a power supply and ground in the multilayer wiring substrate are constituted of a capacitor of high equivalent series resistance (ESR) and a capacitor of low ESR.
PTL 3 discloses a technique in which a capacitor element of high ESR and a capacitor element of low ESR are interposed in parallel and in a polarity inversed manner between a power supply and ground, and on keeping low impedance at a resonance frequency, impedance at an anti-resonance frequency is reduced.
PTL 4 discloses a decoupling circuit reducing internal impedance.